Three-Stage Turbo MBER Multiuser Beamforming Receiver Using Irregular Convolutional Codes

Abstract—Based on extrinsic information transfer (EXIT) charts, the convergence behavior of a three-stage serially concate-nated multiuser beamforming receiver is presented. This system uses a linear minimum bit error rate (BER) multiuser detector as the inner module. Due to the nonrecursive nature of this inner module, a unity-rate memory-1 recursive precoder is placed in front of the channel to provide the required recursive structure. Irregular convolutional codes (IRCCs) are constructed to be used as the outer code to achieve near-capacity performance. Our simulations show that this system outperforms the traditional two-component iterative structure and is capable of significantly reducing the error floor. Index Terms—Beamforming, extrinsic information transfer (EXIT) charts, irregular convolutional codes (IRCCs), minimum bit error rate (MBER). I